Future climate scenarios for a coastal productive planktonic food web resulting in microplankton phenology changes and decreased trophic transfer efficiency

Albert Calbet, Andrey F. Sazhin, Jens C. Nejstgaard, Stella A. Berger, Zachary S. Tait, Lorena Olmos, Despoina Sousoni, Stamatina Isari, Rodrigo A. Martínez, Jean Marie Bouquet, Eric M. Thompson, Ulf Båmstedt, Hans H. Jakobsen

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Abstract

We studied the effects of future climate change scenarios on plankton communities of a Norwegian fjord using a mesocosm approach. After the spring bloom, natural plankton were enclosed and treated in duplicates with inorganic nutrients elevated to pre-bloom conditions (N, P, Si; eutrophication), lowering of 0.4 pH units (acidification), and rising 3°C temperature (warming). All nutrient-amended treatments resulted in phytoplankton blooms dominated by chain-forming diatoms, and reached 13-16 mg chlorophyll (chl) a l-1. In the control mesocosms, chl a remained below 1 μg l-1. Acidification and warming had contrasting effects on the phenology and bloom-dynamics of autotrophic and heterotrophic microplankton. Bacillariophyceae, prymnesiophyceae, cryptophyta, and Protoperidinium spp. peaked earlier at higher temperature and lower pH. Chlorophyta showed lower peak abundances with acidification, but higher peak abundances with increased temperature. The peak magnitude of autotrophic dinophyceae and ciliates was, on the other hand, lowered with combined warming and acidification. Over time, the plankton communities shifted from autotrophic phytoplankton blooms to a more heterotrophic system in all mesocosms, especially in the control unaltered mesocosms. The development of mass balance and proportion of heterotrophic/autotrophic biomass predict a shift towards a more autotrophic community and less-efficient food web transfer when temperature, nutrients and acidification are combined in a future climate-change scenario. We suggest that this result may be related to a lower food quality for microzooplankton under acidification and warming scenarios and to an increase of catabolic processes compared to anabolic ones at higher temperatures.

Original languageEnglish (US)
Article numbere94388
JournalPloS one
Volume9
Issue number4
DOIs
StatePublished - Apr 10 2014
Externally publishedYes

Bibliographical note

Funding Information:
We conducted a land-based mesocosm experiment at the Marine Biological Field Station of the University of Bergen, Norway from June 10 to 30, 2011. The experiment included 4 treatments (control, +eutrophication, +acidification, and +warming; ) in duplicate (A and B; for phytoplankton taxonomy, only replicate A was analysed). This study was a part of a larger experiment hosted by the Nordic Council project BIOPUMP, the EU FP7 project MESOAQUA and a Norwegian Ocean and Coast research grant (see financial disclosure). The light-regime during the mesocosm experiment displayed a 19∶5 day:night cycle with a maximum light intensity on air of ca. 300000 Lux (ca. 5500 μmol photon m sec) measured by HOBO units (Onset Computer Corporation, Bourne, MA, USA). The initial (day 0) underwater light climate within the mesocosms measured at 1 m depths did not show difference between the treatments (ANOVA, p = 0.55). th th −2 −1

ASJC Scopus subject areas

  • General

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